Originally roads, whether paved or unpaved, had illdefined travel paths or lanes so that oppositely traveling vehicles could readily encounter one another or leave the sides of the road.
A certain measure of protection to vehicle drivers and their passengers was afforded by providing a median strip of raised construction between oppositely traveled lanes and/or by providing the sides of the road with a curb or raised portion.
In some cases, the raised portions, intended to guide the vehicle wheels back into the proper travel lane, were prismatic humps, ribs or ridges of concrete anchored to the ground or to the pavement. For the most part, these structures had a height significantly less than half the diameter of the average wheel used by vehicles traveling on the roadway.
Attempts were made to improve upon such structures because, while the concrete ridges had relatively low repair cost and were easily fabricated and mounted, especially during road building operations, they had disadvantages. For example, when the guide ridge was relatively low, the wheel of a wayward vehicle could readily jump the ridge and hence the guiding function was lost or inadequate.
Naturally, attempts were made to utilize prismatic concrete structures of somewhat greater height. With such systems the vehicles did not as readily jump the guide member, but any encounter of the vehicle with the concrete structure could cause considerable damage to the vehicle and to the operator or passenger.
This is a particular disadvantage in the case of roadways traveled by motorcycles and like two-wheel vehicles since any encounter of the vehicle with a concrete barrier of this type almost of necessity will result in an impact between the vehicle user and the structure at an elevated speed with serious injury to the person. It will be readily recognized that any impact between an individual moving at any substantial speed if carried by or thrown from the vehicle, with an immovable concrete object cannot fail to cause significant injury, if not death.
Still another disadvantage of rigid or nonyieldable concrete road barriers is that the significant friction between the wheel and concrete can result in a climbing of the wheel upon the barrier if the angle of attack of the wheel is appropriate, such that the vehicle may leap the barrier or may be overturned by the encounter with obvious drawbacks both for four-wheel and two-wheel vehicles.
Other types of barriers have been described by my previous applications and reference can be made, for example, to my U.S. Pat. Nos. 3,322,390; 3,476,549; 3,603,562; 3,704,061; 3,784,167; 3,963,218; 3,881,697; 3,966,173 and 4,047,701, and in the documents or references cited or made of record therein.
Particular attention is directed to the system of German Pat. No. 20 26 225 which, like some of the United States patents mentioned, describes a road barrier in which the guide planks are spaced above the ground or road surface on posts which are longitudinally separated along the direction of travel, the barrier or plank being formed as a hollow sheet-metal profile filled with a synthetic-resin foam. An advantage of this type of road barrier is that the plank is both flexible and stable, operating without a significant rebound tendency so that a slingshot return of the vehicle into the travel lane is avoided while the kinetic energy is dissipated as the vehicle slides along the yieldable length of the rail.
Because of the yieldability of these rails, the likelihood of damage to the vehicle and even to operating personnel or passengers is seriously diminished by comparison with rigid concrete structures.
Nevertheless, since rigid posts were generally provided at spaced apart locations along such a rail, to support it above the ground, there was always the danger that the impact of an operator or a passenger with the rail could cause some injury analogous to that which occurs upon an encounter with a concrete structure.
A further disadvantage of earlier types of flexible-rail systems is the unesthetic appearance of them and the fact that especially at night the posts, and spaces between the posts, cooperate with the headlights of the vehicles to disturb the concentration of the driver. An object of this invention is to overcome these disadvantages.